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std::make_unique

From cppreference.com
< cpp‎ | memory‎ | unique ptr
 
 
 
 
 
Defined in header <memory>
template< class T, class... Args >
unique_ptr<T> make_unique( Args&&... args );
(1) (since C++14)
(only for non-array types)
template< class T >
unique_ptr<T> make_unique( std::size_t size );
(2) (since C++14)
(only for array types with unknown bound)
template< class T, class... Args >
/* unspecified */ make_unique( Args&&... args ) = delete;
(3) (since C++14)
(only for array types with known bound)

Constructs an object of type T and wraps it in a std::unique_ptr.

1) Constructs a non-array type T. The arguments args are passed to the constructor of T. The function does not participate in the overload resolution if T is an array type. The function is equivalent to:
unique_ptr<T>(new T(std::forward<Args>(args)...))
2) Constructs an array of unknown bound T. The function does not participate in the overload resolution unless T is an array of unknown bound. The function is equivalent to:
unique_ptr<T>(new typename std::remove_extent<T>::type[size]())
3) Construction of arrays of known bound is disallowed.

Contents

[edit] Parameters

args - list of arguments with which an instance of T will be constructed.
size - the size of the array to construct

[edit] Return value

std::unique_ptr of an instance of type T.

[edit] Exceptions

Any exception thrown by the contructor of T. If an exception is thrown, this function has no effect.

[edit] Example

#include <iostream>
#include <memory>
 
struct Vec3
{
    int x, y, z;
    Vec3() : x(0), y(0), z(0) { }
    Vec3(int x, int y, int z) :x(x), y(y), z(z) { }
    friend std::ostream& operator<<(std::ostream& os, Vec3& v) {
        return os << '{' << "x:" << v.x << " y:" << v.y << " z:" << v.z  << '}';
    }
};
 
int main()
{
    // Use the default constructor.
    std::unique_ptr<Vec3> v1 = std::make_unique<Vec3>();
    // Use the constructor that matches these arguments
    std::unique_ptr<Vec3> v2 = std::make_unique<Vec3>(0, 1, 2);
    // Create a unique_ptr to an array of 5 elements
    std::unique_ptr<Vec3[]> v3 = std::make_unique<Vec3[]>(5);
 
    std::cout << "make_unique<Vec3>():      " << *v1 << '\n'
              << "make_unique<Vec3>(0,1,2): " << *v2 << '\n'
              << "make_unique<Vec3[]>(5):   " << '\n';
    for (int i = 0; i < 5; i++) {
        std::cout << "     " << v3[i] << '\n';
    }
}

Output:

make_unique<Vec3>():      {x:0 y:0 z:0}
make_unique<Vec3>(0,1,2): {x:0 y:1 z:2}
make_unique<Vec3[]>(5):   
     {x:0 y:0 z:0}
     {x:0 y:0 z:0}
     {x:0 y:0 z:0}
     {x:0 y:0 z:0}
     {x:0 y:0 z:0}

[edit] See also

constructs a new unique_ptr
(public member function) [edit]